This study investigates the structural, morphological, optical, and electro-optical characteristics of Pb(Zr0.52Ti0.48)O3 (PZT) thin films deposited on fluorine-doped tin oxide (SnO2:F, FTO) substrates using a custom-made radio frequency (RF) magnetron sputtering system. The films were grown at a substrate temperature of 300 oC and subsequently annealed at 650 oC for 1 hour in a muffle furnace in an air ambient to promote crystallization and phase formation. XRD analysis confirms the formation of polycrystalline perovskite PZT with a preferred (110) orientation, average lattice constant of 4.09 Å, and average crystallite size of 37.06 nm. SEM analysis reveals a homogeneous granular surface morphology with grain sizes ranging from 95 to 105 nm, while EDS analysis verifies a Zr/Ti atomic ratio of 51.9/48.1, closely matching the morphotropic phase boundary (MPB) composition of the PZT in the target. Optical transmittance measurements show approximately 80% transmittance in the visible region, and Tauc’s plot analysis yields a direct bandgap of 3.35 eV for the annealed film, representing a significant blue shift compared to the 2.66 eV bandgap of the as-deposited film. The transient photocurrent measurements carried out under the Hg-Xe light excitation reveal an increase from picoampere level (dark) to 17 nA (illuminated), with rise and fall times of ∼ 130 ms. The results demonstrate that RF magnetron sputtering combined with appropriate thermal treatment produces high-quality PZT thin films, which can be suitable for ultraviolet (UV) optoelectronic applications.
The Ti50Ni39Zr10Nb1 (at.%) shape memory alloy was heat treated at 873 K, 1073 K, and 1273 K, followed by ice-water quenching. The effects of heat treatment on phase transformation behavior, crystal structure, and mechanical properties were investigated. The differential scanning calorimetry (DSC) analysis determined the transformation enthalpy, entropy, elastic strain energy, and Gibbs free energy changes. The X-ray diffraction (XRD) results indicated grain refinement and improved crystallinity after heat treatment.Vickers hardness values increased compared to the as-cast condition. The results reveal that both austenite and martensite transformation temperatures increase after heat treatment, with the most pronounced rise observed at 1273 K. It was demonstrated that the heat treatment temperature leads to an increase in hysteresis. Moreover, it is noticeable that both the Gibbs free energy and elastic energy significantly increase after the heat treatment process. In addition, it was observed that increasing the heat treatment temperature significantly increased the microhardness. These results show that heat treatment significantly modifies the transformation characteristics and microstructure of the alloy, leading to improved mechanical and functional properties.
The International Astronomical Union 2015 Resolution B2 (IAU2015GARB2) has resolved the long-standing problem of zeropoint constants for the absolute and apparent bolometric magnitude scales and opened a new window in fundamental astrophysics. The empirical zero-point constants of the bolometric corrections, 𝐶2 (𝜉), and the absolute/apparent magnitudes, 𝐶𝜉 /𝑐 𝜉 , for the Gaia passbands were obtained from 88 Gaia XP spectra, and absolute bolometric/filtered magnitudes. The individual zero-pointconstants ⟨𝐶2⟩ of the bolometric corrections (𝐵𝐶𝜉 ) for each star revealed weighted averages of ⟨𝐶2 (𝐺)⟩ = 0.8677 ± 0.0109 mag, ⟨𝐶2 (𝐺BP)⟩ = 1.0449 ± 0.0116 mag, and ⟨𝐶2 (𝐺RP)⟩ = 2.0510 ± 0.0087 mag. Furthermore, 𝐶Bol = 71.197425... mag and 𝑐Bol = −18.997351...mag announced by IAU2015GARB2, and using the definition of 𝐶2 = 𝐶Bol − 𝐶𝜉 = 𝑐Bol − 𝑐 𝜉 ,where the subscript 2 indicate the wavelength ranges of two in which one is for bolometric and the other for one of the three filters, the zero-point constants of magnitudes for Gaia filters as 𝐶G = 70.1525 ± 0.0109 mag and 𝑐G = −19.8651 ± 0.0105 mag, 𝐶GBP = 70.1525±0.0116 mag and 𝑐GBP = −20.0423±0.0116 mag, and𝐶GRP = 69.1464±0.0087 mag and 𝑐GRP = −21.0484±0.0087 mag, if 𝐿𝜉 and 𝑓𝜉 are in SI units, assuming no extinction. Lastly, spectroscopic 𝐵𝐶s for Gaia magnitudes of 88 stars and the spectroscopic 𝐵𝐶 − 𝑇eff relation for each Gaia filter are presented.
The International Astronomical Union 2015 Resolution B2 (IAU2015GARB2) has resolved the long-standing problem of zeropoint constants for the absolute and apparent bolometric magnitude scales and opened a new window in fundamental astrophysics. The empirical zero-point constants of the bolometric corrections, 𝐶2 (𝜉), and the absolute/apparent magnitudes, 𝐶𝜉 /𝑐 𝜉 , for the Gaia passbands were obtained from 88 Gaia XP spectra, and absolute bolometric/filtered magnitudes. The individual zero-pointconstants ⟨𝐶2⟩ of the bolometric corrections (𝐵𝐶𝜉 ) for each star revealed weighted averages of ⟨𝐶2 (𝐺)⟩ = 0.8677 ± 0.0109 mag, ⟨𝐶2 (𝐺BP)⟩ = 1.0449 ± 0.0116 mag, and ⟨𝐶2 (𝐺RP)⟩ = 2.0510 ± 0.0087 mag. Furthermore, 𝐶Bol = 71.197425... mag and 𝑐Bol = −18.997351...mag announced by IAU2015GARB2, and using the definition of 𝐶2 = 𝐶Bol − 𝐶𝜉 = 𝑐Bol − 𝑐 𝜉 ,where the subscript 2 indicate the wavelength ranges of two in which one is for bolometric and the other for one of the three filters, the zero-point constants of magnitudes for Gaia filters as 𝐶G = 70.1525 ± 0.0109 mag and 𝑐G = −19.8651 ± 0.0105 mag, 𝐶GBP = 70.1525±0.0116 mag and 𝑐GBP = −20.0423±0.0116 mag, and𝐶GRP = 69.1464±0.0087 mag and 𝑐GRP = −21.0484±0.0087 mag, if 𝐿𝜉 and 𝑓𝜉 are in SI units, assuming no extinction. Lastly, spectroscopic 𝐵𝐶s for Gaia magnitudes of 88 stars and the spectroscopic 𝐵𝐶 − 𝑇eff relation for each Gaia filter are presented.
The spectral evolution of asteroid surfaces reflects the competition between space weathering and impact resurfacing. While previous studies focused primarily on age-dating, the role of family population size remains largely unexplored. We tested whether population-dependent collisional activity affects observable surface properties by analyzing 154 asteroid families using NEOWISE thermal infrared photometry, validated by independent AKARI observations and error propagation analysis. We introduced the V-Dominance Index (VDI) to quantify the incidence of extreme resurfacing signatures within families, defined as the fraction of members with visible-to-infrared albedo ratios p_V/p_IR > 1.2. Among tested parameters, family population size (N) emerged as the dominant correlate of VDI across both silicaceous (S-complex: r_s = 0.58) and carbonaceous (C-complex: r_s = 0.44) taxonomic types, with a full-sample correlation r_s = 0.476 (p = 4.31 x 10^-10). This correlation survived Monte Carlo permutation tests, binomial null model validation, age-matched contrast analyses, and heliocentric independence tests. Percentile sensitivity analysis demonstrated that VDI isolates rare resurfacing events detectable only at extreme thresholds. In families older than 2 Gyr, large populations maintained statistically significant fresh tails (p < 10^-4), whereas small populations were saturated. These results indicate that massive families experience elevated collisional resurfacing rates that counteract space weathering saturation.
We present a comprehensive photometric and spectroscopic study of the triple stellar system EM Boo. The system is composed of detached, low-mass components, and for the first time in the literature, the spectrum of the tertiary component has been successfully disentangled from the composite spectrum using the code. Synthetic spectra were generated for each disentangled component, allowing determination of their atmospheric parameters. The depth of the H_α line in the tertiary spectrum indicates that it is an intermediate-temperature star, consistent with spectral types between A and F, and its effective temperature was determined to be 7000 K. By analyzing the radial velocity and light curves simultaneously, the fundamental physical parameters of the system were derived, and its detailed evolutionary status was investigated using models. The HIPPARCOS trigonometric parallax (ϖ_ Hip=1.33±1.45 mas) and Gaia DR3 trigonometric parallax (ϖ_ Gaia=3.9699±0.1812 mas) show a significant discrepancy, most likely related to the system's multiplicity and the limitations of single-star astrometric solutions. To provide independent distance estimates, we modeled the spectral energy distribution (SED) using multi-wavelength flux data, yielding E(B-V)=0.05 mag and a trigonometric parallax ϖ_ SED=3.2 mas, corresponding to d_ SED=313 pc. Furthermore, photometric distance estimates based on the components' absolute magnitudes yield d_1=299 pc and d_2=301 pc, in good agreement with the SED-based distance. Both the SED-based and photometric distances converge around d=300 pc, indicating that the Gaia trigonometric parallax underestimates the true distance of EM Boo.
We present a physically motivated spectral energy distribution (SED) modelling framework for deriving stellar and circumstellar disc parameters from broadband photometry. The model combines a parametrized disc structure, dust opacity, and interstellar extinction within a Bayesian Markov Chain Monte Carlo (MCMC) inference scheme, allowing correlated parameters to be constrained self-consistently. Initial parameter estimates are obtained via non-linear least-squares fitting and subsequently refined through MCMC sampling. The method is first validated using the well-studied debris disc system 49 Cet, for which the model successfully reproduces key literature properties. It is then applied to the previously uncharacterised young stellar object (YSO) candidate 2MASS J02512618+6012576, using photometric measurements compiled from multiple surveys. The resulting fit indicates a late-type pre-main-sequence star surrounded by a substantial circumstellar disc consistent with a moderately embedded Class II object. We further assess the sensitivity of the inferred parameters to the adopted extinction law and find that the high reddening required by the model is robust against variations in R_V. This work demonstrates that physically meaningful constraints on disc structure can be obtained from broadband SED modelling when extinction and distance are treated within a statistically consistent framework.
The spin periods of magnetars and X-ray dim isolated neutron stars (XDINS) cluster within a remarkably narrow range. Using the current sample of 30 magnetars with measured periods (ranging from 0.33 to 11.78 s) and 8 XDINS (ranging from 3.45 to 12.76 s), we utilize the point-likelihood technique to constrain the birth and final periods of these sources, assuming a steady-state population. Employing a general braking law characterized by a constant braking index n, we find that for n > 2 the final (cut-off) period of magnetars is constrained to P_f ≃ 11.8 - 12.0 s and XDINS to P_f ≃ 12.8 - 14.9 s, at the 95 per cent confidence level, while the birth periods remains largely unconstrained for dipole spin-down (n=3) as in earlier work. The slight increase in the upper cutoff from ∼12 to ∼15 s over two decades of discoveries of new sources, yielding a threefold increase in the known magnetar population, and the extension of the minimum period to ∼ 0.33 s strongly support a physical origin for this clustering. We discuss this result in the context of magnetic-field-decay models and fallback-disc torque-equilibrium scenarios. The combined magnetar and XDINS sample (38 sources) yields the tightest constraints on P_f≃ 12.8-12.9 s, for n=3, suggesting possible evolutionary connections between these populations and pointing toward a common physical mechanism that terminates the observable phase of these neutron stars at periods near 14 s.
On 29 March 2006, a total solar eclipse was observed in the Manavgat district of Antalya, Turkey. During the event, the solar corona was observed using an 8-inch mirrored telescope. White-light polarization observations were carried out at three distinct angles using a polarizing filter placed in front of the camera system. To calibrate the intensity of the roll film, photographs of the eclipse and the solar disk were taken with a traditional 35mm manual camera. Using the solar disk images obtained during the eclipse, an intensity calibration curve for the roll film was created. This curve was then used to calculate various physical properties of the solar corona, including intensity, degree of polarization, electron density, and mean temperature. The results of these calculations were compared with the corona models developed by and , as well as with findings from other researchers. Except for the degree of polarization, the measured physical parameters closely match the values given in the literature.
Eclipsing binary systems play a vital role in astrophysics, as they provide a direct means of measuring fundamental stellar parameters. By combining high-precision space-based observations with ground-based multicolor photometric data, these parameters can be determined with greater accuracy. In this study, we present the first photometric analysis of the IY Aur eclipsing binary system, using a combination of the Transiting Exoplanet Survey Satellite (TESS) light curve and new UBVRI CCD observations obtained with the 60 cm robotic telescope (T60) at the TUBITAK National Observatory. Through detailed photometric modeling, the masses and radii of the system's primary and secondary components were determined as M_1=6.51± 0.81 M_⊙, M_2=5.39± 0.87 M_⊙, and R_1=4.15± 0.20 R_⊙, R_2=6.88± 0.33 R_⊙, respectively. The logarithmic values of luminosity and surface gravity were calculated as log L_1=3.14± 0.20 L_⊙ and log g_1=4.01± 0.02 cgs for the primary component, and log L_2=2.50 ± 0.22 L_⊙ and log g_2=3.49± 0.03 cgs for the secondary component. Furthermore, the distance to IY Aur was estimated as d=1690±237 pc.
This study examines the period variation of the eclipsing binary system KR Cyg, a near-contact binary characterized by its short orbital period and significant stellar interactions. The precise orbital parameters of the system have been determined through light curve data collected periodically since 1999 and were published in our previous studies. Additionally, minimum light observations have been continuously monitored to analyze the period variation of the system. In our earlier work, the masses of the primary and secondary components were determined as 2.88±0.20 M_⊙ and 1.26± 0.07 M_⊙, with corresponding radii of 2.59± 0.06 R_⊙ and 1.80± 0.04 R_⊙. The bolometric albedo and effective temperature of the less massive star were also investigated, and deviations caused by mutual illumination effects were identified. These results provide valuable insights into the evolutionary status of KR Cyg and shed light on the dynamic processes that occur in near-contact binary systems. Using updated eclipse timings, an (O-C) diagram was constructed, revealing both long-term trends and periodic oscillations. These cyclical variations are thought to indicate the presence of a tertiary component affecting the system via the light-time effect. Additional observations and modeling are recommended to confirm the tertiary hypothesis and further refine the parameters of the system.
In this study, colour-magnitude relations (CMRs) for DA-type white dwarfs in the Sloan Digital Sky Survey (SDSS) photometric system were investigated. For this purpose, the SDSS data for 20,247 white dwarf stars, as provided in the study by Anguiano et al. (2017), were matched with the Gaia third data release (Gaia DR3) catalogue to obtain trigonometric parallax (ϖ) data. The SDSS ugriz magnitudes of the stars were corrected for interstellar extinction using dust maps provided for the Milky Way, and distances from the Sun to the stars were calculated. The SDSS magnitudes were thus corrected for the effects of interstellar extinction. For the calibration of the stars, 5,516 white dwarf stars were selected, with apparent magnitudes brighter than g_0=21 mag and relative parallax errors measured to better than σ_ϖ/ϖ=0.1. Subsequently, three separate CMRs were derived for the absolute magnitudes M_ g, M_ r, and M_ i, each calibrated to two-colour indices. The coefficient of determination (R^2) of the obtained CMRs are highly reliable in the bf range of 0.86 to 0.95. Moreover, the standard deviations of the differences between the absolute magnitudes obtained from the relations and the original ones of the calibration stars range from 0.26 to 0.37 mag.
The development line of bolometric corrections within the brief history of photometry was described from the perspective of the Kuhnian philosophy of science. The luminous efficiency and heat index were two previous concepts to imply visual and bolometric brightness difference of a star, which was mainly suggested and used as auxiliary tools for calibrating stellar temperature scales before the term “bolometric correction” (BC) was also introduced for the same purpose by Kuiper in 1938, as BC = M_ bol - M_ V = m_bol - V. Despite its ill-posed nature imposing no zero-point constant (C_2=0) for the BC scale and L_ V = L × 10^BC/2.5, if BC>0, L_ V is unphysical, for the luminosity of a star from which “BC of a star must always be negative,” “the bolometric magnitude of a star ought to be brighter than its V-magnitude,” and “the zero point of bolometric corrections are arbitrary” (paradigms) were extracted. The newest of the first three definitions of BC was accepted and used throughout the century. Therefore, the part of the development line of BC before Kuiper could be considered a prescience period. The rest could be named the normal science period in which astrophysicists work under the three paradigms. The rise of BC as a concept, how the ill-posed definition BC emerged/used, how inconsistencies (paradigms) of BC developed, and how the Resolution B2 of the General Assembly of the International Astronomical Union imposing C_ bol = 71.197 425 … mag, and C_2>0, for the zero-point constants of the M_Bol and BC scales resolve the long-lasting problems were discussed. Generalized new definition of BC implying L_ V=L × 10^( BC-C_2)/2.5 were given to replace L = L_ V× 10^BC/2.5.
We conducted an in-depth analysis of NGC 6793 open cluster via Gaia DR3 data, including astrometric, spectroscopic, and photometric measurements. Selection of 147 stars, which show membership probabilities P≥0.5 were classified as likely members. The mean trigonometric parallaxes and proper-motion components of the cluster were found to be ϖ = 1.674 ±0.045 mas and (μ_αcosδ, μ_δ) =(3.814±0.031, 3.547±0.034) mas yr^-1. Fundamental astrophysical parameters of NGC 6793 are derived simultaneously as t = 650 ± 50 Myr, μ = 9.508±0.070 mag, and E(G_ BP-G_ RP) = 0.361 ± 0.035 mag. Additionally, the cluster's luminosity function analysis reveals the G-absolute magnitude limit of the most likely stars, indicating a well-defined stellar population. The total mass of the cluster, determined through the mass function (MF) and considering stars with membership probabilities P ≥ 0.5, was estimated as 139 ± 12 M/M_⊙. The slope of the MF was found to be Γ = 1.40 ± 0.26, a result consistent with the Salpeter value. The kinematic analyses present velocity ellipsoid parameters as well as the convergent point (A_ o, D_ o) = (85^∘.85 ± 0^∘.11, 3^∘.12 ± 0^∘.57). Analyses have shown that it is moving in a box-shaped orbit beyond the Sun's galactic radius and belongs to the thin disk population of the Milky Way. The calculated relaxation time suggests that NGC 6793 has reached a dynamically relaxed state, where the dynamical evolution parameter τ significantly exceeds one. These results highlight both the cluster's internal stability and its connection to the thin disc population.
